Psoriasis is a disease for which new modalities of treatment are needed, especially for chronic, plague-type lesions with limited skin distribution. Patients and physicians alike are frustrated because none of the existing therapies is completely satisfactory. Preliminary clinical studies indicate that psoriatic plaques, like cancer tumors, may be cleared as a result of being heated to temperatures in the hyperthermic range (42 - 46 degrees C). Proposed is the development of a relatively simple and inexpensive hyperthermia system capable of treating lesions of psoriasis and other heat-sensitive skin diseases. Under Phase I, a family of low-loss, extremely wideband treatment applicators was developed. A significant feature of the design is that transducers with shapes and sizes well suited for treating those body parts most often affected by psoriasis can be fabricated. Initial patient trials and dosimetry studies indicate that tailored thermal distributions can easily be induced in psoriatic tissues. Phase II seeks to develop a microprocessor-controlled electronics package capable of dynamically and simultaneously controlling the acoustic frequency and power output of the ultrasound transducer and the temperature of the water cuff that couples the energy to the body, and to enter clinical trials at four research institutions. From these investigations, it is anticipated that optimized treatment protocols will emerge that confirm the safety and efficacy of this new therapy, and thereby create a demand for commercial systems.